Does the “sting” mean it worked &no-feeling mean it didn’t?

I had my first laser treatment on several areas, some of which really stung (armpits & bikini) and some where I couldn’t feel a thing (thighs & forearms).

Does whether or not you can feel the treatment indicate its effectiveness?

of course pain is going to differ in different areas of the body because some places eg bikini area are more sensitive than others eg thighs!

Sure, greater feeling in sensitive areas like the bikini & armpits is naturally to be expected, but in several areas (knees, thighs & forearms), I couldn’t feel a single thing AT ALL (as if absolutely nothing was being done) while the armpits were almost unbearable (and are ironically, the area showing fall-out since the treatment 2 weeks ago).

If the laser is penetrating my skin and actually killing cells, shouldn’t I be able to feel SOMETHING in every area (even the thicker/tougher skinned areas like forearm, thigh & knee)?

You should feel a “zing” during treatment on tough areas, but even if you don’t, it doesn’t necessarily mean the treatment was ineffective. You should have a time period of relatively no/or little hair growth, then some re-growth right before your next scheduled treatment.